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How To Degree A Camshaft

* This page was designed for the Ford Escort SPI / CVH / SEFI engines. The same basic proceedure can be used on the Zetec or any other engine. You have to be able to read tappet or valve lift, find exact top dead center, and use a degree wheel on the crankshaft. With the Zetec engine you may use the adjustable camshaft drive sprockets to adjust the valve timing since they are available. You can also move the exhaust cam in relation to the intake cam to alter the power curve. This changes the lobe center spread and overlap. (Don't attempt this unless you know exactly what you are doing or serious engine damage could result). Lobe center spreads can run from about 104 degrees to about 116 degrees. Most engine combinations run best from 108 degrees to 112 degrees.

You here people say that if the cam is made right if will fit right. WRONG! But if you don't check, you'll never know. Ok, we've all heard of production tolerances. Say, the camshaft keyway is cut .001" off, the cam pulley may be another .001" off. Then the key may fit slightly loose and allow the pulley to turn back a little more. And on the bottom end, the crankshaft keyway may be slightly out of spec, and the keyway in the pulley on the crank snout, and again a possibly loose fitting key or one that is worn from use. These tolerences can really stack up against you.

And there is the rubber belt. Belts stretch with use and age. Belts cannot be made exactly precise due to the way they are manufactured. As the belt stretches, the cam timing retards.

Then, if the head is milled or if the head gasket is not as thick as the stock one, the cam timimg gets retarded. This is because the distance from the cam to the crank decreases, but the drive side of the belt stays the same, so the cam gets shifted backwards. And don't even thing about offsetting the belt by a tooth. One tooth at the cam is about 19 crank degrees.

Sometimes the auto manufacturer will decide that the cam needs to be set a certain way for emissions or whatever. Most aftermarket cam manufactures think cams run best advanced. So that's the way they grind them. While this works very well in most V-8 engines, it doesn't work with this 4-cylinder engine.

Ford Escort SPI, SEFI, CVH

Basic timing belt drive layout for the Escort CVH engines.

The worst case I have personally seen was almost 16 degrees out by just installing the cam as it came and aligning the dots. Needless to say, the owner was not pleased with the performance as the car ran quite a bit slower than it did with the stock cam. Was something wrong with the cam? NO! Just a problem with the installer! When it was degreed in properly, the car ran over a full second quicker than it had previously in the quarter mile.

Lube and install the camshaft in the engine, or head, using a new timing belt or chain and gears. Align the cam using the dots on the gears, head, or block. Mount the degree wheel to the crankshaft and the pointer to the block. Make sure the pointer is secure and doesn't move. If you ever bump it, reset it. For the Escort CVH/SPI engines, download and print the degree wheel. Print if on heavy paper, cut out, and glue it to the pulley. Make sure it prints to 5-11/16" diameter. Click here to download. See picture #1 below.

Now we must find exact top dead center (TDC). There are several ways to do this. The easiest way is to use a piston stop screwed in through the #1 cylinder spark plug hole. Make sure the #1 piston is not all the way up in the bore.

CAUTION!!!   You MUST disconnect the battery and remove the rocker arms on #1 cylinder before installing the piston stop. If the engine were to be turned over it could put a hole in the piston and it's possible for the valves to contact the piston stop if they open. Turn the engine over by hand slow and easy. It will be easier if you take all the spark plugs out first.

Rotate the crankshaft slowly to the right until you feel it contact the piston stop. Now mark location of the degree wheel. Next, turn the crankshaft to the left until it contacts the piston stop again. Mark the location. Backup the crankshaft to move the piston away from the piston stop. Then remove the piston stop from the head. Half way between the two marks is exact (TDC). Reposition the degree wheel and/or pointer and recheck. I have seen factory TDC marks up to 8 degrees off.

Next we need to set up a dial indicator to read the movement of the #1 cylinder's lifter movement. The indicator must be in alignment with the angle of the lifter. If not, the readings will be inaccurate. It's usually better to find a method to attach the dial indicator stand with a bolt to the head. There isn't enough steel anywhere for a magnetic base to hold. You will need to set up on the intake lifter and later the exhaust lifter. See picture #2 below.

When taking readings, it's important to always turn the engine over clockwise. This is the direction the engine runs and it keeps he drive side of the belt tight. Turn the crankshaft until the lifter reaches the bottom of it's travel. This is called the "base circle" of the cam. Set the indicator to read "0" here. You will see that the crankshaft rotates twice for every time the camshaft rotates.

Turn the crank slowly until the intake lifter rises .050" from the base circle. Most performance cams are spec'd at .050" and .006" tappet/lifter lift. I prefer the .050" method as this gives a better indication of the lobe profile. Write down the reading from the degree wheel. This will read as "degrees before top dead center" or (BTDC) and may be a negative number on a short duration cam. Next turn the crankshaft and read the maximum lifter rise. The hand on the dial indicator will turn several times so be sure to keep track. Most dial indicators have a second hand that tells revolutions. Then keep turning the crankshaft until the dial indicator reads .050" from the base circle and write this figure down. This will read as "degrees after bottom dead center or (ABDC).

Next, setup on the exhaust lifter and repeat the complete procedure. This time the opening figures will be "degrees before bottom dead center" or (BBDC) and the closing figures will be "degrees after top dead center" or (ATDC). This also may be a negative number on a short duration cam.

EXAMPLE:  (A stock 1998 SPI Ford cam)

Intake open (-24) degrees BTDC
Intake close (27) degrees ABDC
Intake lobe lift (.2435")               

Exhaust open (21) degrees BBDC
Exhaust close (-15) degrees ATDC
Exhaust lobe lift (.2435")

* To figure the actual valve lifts, multiply the lobe lift by the rocker arm ratio. All Escort CVH/SPI engines used a 1.65/1 ratio. With the example above, this gives you a .402" lift at the both valves.

* To find the duration add the opening and closing numbers (even if it's a negative number) plus 180. Do this for the intake and exhaust lifters. With the example above, we get 183 degrees on the intake and 186 degrees on the exhaust at .050" lift.

* To find the theoretical intake lobe centerline, divide the duration by 2 and subtract the opening number. This gives us 115.5 degrees BTDC.  For the exhaust, divide the duration by 2 and subtract the closing number. And we get 108 degrees (ATDC). Add the intake and exhaust figures and divide by 2. This gives us the lobe center spread. (115.5 + 108 = 223.5, divide by 2 = 111.75 degree lobe centers)..

Picture #1

Ford Escort SPI crankshaft pulley

* If the intake centerline is less than the exhaust, the camshaft is installed advanced by that amount. If the exhaust centerline is less than the intake as we have in the example, it is installed in a retarded position that amount. (115.5 minus 108 = 7.5 degrees, divide this by 2 = 3.75 degrees retarded).

* A few cam manufacturers recommend the intake lobe centerline method. If so, set up the dial indicator on #1 intake lifter. Readings are taken when the lifter has dropped .050" from the maximum lift on each side of the lobe. Halfway between these two points is the lobe centerline

NOTE: Advancing or retarding the cam changes the torque curve up or down in rpm's. Advancing the cam timing usually moves the torque curve down a bit at the expense of top end. Retarding the cam timing usually does the opposite. Normally going over 6-8 degrees one way or the other hurts overall power. Almost every cam we have tested in the Escort CVH / SPI engines performs the best at 4 degrees retarded regardless of what the cam manufacturer suggest. Also, advancing a cam decreases the intake valve to piston clearance. Retarding decreases the exhaust valve to piston clearance so on a large cam, you should check these. A stock lifter and a light checking spring is the easiest way to do this. The spring is just enough to hold the valve shut. Then install the rocker arm and rotate the engines slowly by hand. You can press the valve down with you finger to check the clearance. Do this every few degrees until you find the closest spot. A minimum of .060" is required for safe operation.

There are several ways to alter the cam timing. An adjustable cam drive gear like our #1C4G11C, made for the SEFI / SPI Ford Escort and Ford Focus SPI engines, is the easiest. Keep in mind the sprocket must match the timing belt on the engine. All Escort engines made since April 1991 use a round tooth belt and must use matching cam drive gear. To adjust the cam timing you simply unloosen the 4 cap screws, rotate the center hub (and camshaft) to the proper location, and retighten the cap screws. Always recheck your readings after each adjustment. See picture #3 at right.

Degreeing the cam sounds difficult but is fairly easy. The setup takes the longest time. Take your time and check the readings several times and you will be fairly accurate. There can be up to 10-20 hp hiding here so it's definitely worth your time and efforts.

Picture #2

degreee a cam

Picture #3

1C4G11C adjustable cam gear

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